In U.S. Pat. No. 3,740,994, assigned to the present assignee and entitled Three-Stage Medical Instrument, a novel cartridge and instrument for ligating, suturing and dividing organic tubular structures by means of surgical staples are disclosed. The present invention relates to an instrument which, together with a cartridge such as disclosed in the commonly assigned patent, is similarly capable of mechanically and repetitiously ligating, suturing and dividing organic tubular structures, such as blood vessels and the like.
The instrument of the present invention is adapted to associate with a cartridge which operates in three stages such as disclosed in the commonly assigned patent. Once the tubular structure is inserted within the area of its jaws, the cartridge wrap, or main body of the cartridge, is moved forward and toward an anvil assembly fixed on the instrument, thereby enclosing the tubular structure within the jaws of the cartridge. Then, a pair of pusher elements is advanced along respective fixed rail assemblies and urge a pair of staples toward respective anvil assemblies. At the forward portion of the pusher stroke, the respective staples encircle the tubular structure at spaced locations and crimp about the structure in such a manner that the tubular structure is sealed at two locations. Finally, and with the pushers at the forwardmost portions of their strokes, a knife blade advances and divides the tubular structure intermediate the two staples.
The instrument disclosed in the commonly assigned patent is also of three-stage design. The forward end of the instrument is provided with three saddles which associate, respectively, with the cartridge wrap, the pushers and the knife of the three-stage cartridge. Three spring elements are housed in the instrument and, in conjunction with a trigger element, operate the cartridge wrap, the pushers and the knife through the three saddle elements. With a cartridge mounted on the instrument, the initial squeezing of the handle moves the cartridge wrap toward the fixed anvil assemblies, and the further squeezing overcomes the force exerted by one of the springs and advances the pushers toward the respective anvils and ultimately, after overcoming the force exerted by another of the springs, urges the knife toward the front of the instrument to effect a cutting operation.
Because of the three-stage operation which depends upon the interaction of three biasing springs, the forces which need to be exerted on the handle of the instrument of the commonly assigned patent are large, and vary with the handle depression. Further variance in the required operating forces is caused by the distinct operations of the cartridge. To eliminate the distance "feel" in the hand of the surgeon that differential forces are required of him, the instrument disclosed in the commonly assigned patent is provided with a variable cam element operating between the power shafts of the instrument and the handle thereof. The cam surface is contoured in such a manner that the force required to operate the handle is relatively constant notwithstanding variations in the required force inputs to the cartridge. In this manner, the surgeon is unaware that three distinct stages of operation occur each time he actuates the instrument.
While the known surgical instrument described in the commonly assigned patent operates satisfactorily, there is room for improvement, particularly with respect to the spring biasing of the saddles.
It is accordingly one object of the present invention to provide a surgical instrument which overcomes the problems of the prior surgical instruments which are noted above.
Yet another object of the present invention is to provide a three-stage surgical instrument adapted to associate with a cartridge and to function, together with the cartridge, to ligate, suture and divide tubular organic structures.
Yet a further object of the present invention is to provide a simple hand-operated instrument adapted for three-stage operation without the necessity for overcoming large spring biases.
A further object of the present invention is to provide a surgical instrument having a simple mechanical linkage which positively controls the operation of a three-stage staple-carrying cartridge.
Still another object of the present invention is to provide a surgical instrument which makes effective use of the mechanical advantage developed by a simple linkage mechanism for controlling the operation of a staple-carrying cartridge.
Yet another object of the present invention is to provide a surgical instrument wherein relative movement between cartridge control elements is provided without biasing springs by means of a shifter dog arrangement.
These and other objects of the present invention, as well as many of the attendant advantages thereof, will become more readily apparent when reference is made to the following description taken in conjunction with the accompanying drawings.